LM3914 - usage, tips?

[egasimus]

I've looked at the Glass Blower GTi, but I'm still not really sure about how to interface the LM3914 with the simple buffer I'm working on.

1. The signal. I just take it with a resistor from the output, half-wave rectify, filter, and give it to the 3914's SIG pin, right?
2. Reference. The LM3914 is inherently linear, and can't indicate dB's on its own, right? Bummer. I've been considering referencing it to 0.775V and having a buffer with an actual dBu meter. Is that even feasible, or will my guitar signal stay in the low decibels unless I crank the hell out of it? If not, can you point me to a simple circuit to convert a linear signal to an exponential one?
3. ...damn, I forgot. Will probably remember what it was when I'm away from the computer, and it's gonna bug me for the rest of the evening.

[Processaurus]

The LM3915 has a log response with 3 db steps, and the LM3916 might be the best for your application, it has a special response especially for audio VU meters that is coarser in the low levels and gets more resolution towards 0db.  It goes -20db, -10, -7, -5, -3, -1, 0, +1, +2, +3.

You actually don't need to rectify or filter if you just want a meter, the chips have an internal half wave rectifier, and in dot mode, the audio is fast enough that it looks like a bar.  Take a look at the app notes in the datasheet, those chips can be very simple to use, pretty much the chip, LEDs, and a couple support components.

[egasimus]

Cool Too bad I ordered a couple of 3914s already. And the place I ordered them from doesn't have any 3915s or 3916s in stock, either. Bummer. :/

Anyway, I remember what number 3 was. The datasheet mentioned:

"Slow"—fade bar or dot display (doubles resolution)

Doesn't seem like I'm gonna have room on my PCB for that, but how is it implemented? 2x LM391x driving a single set of 10 LEDs through resistors?
And number 4 is just an idea - a clipping indicator with a 555 timer connected in place of the 10th led, which will drive the actual led for a second or two. I'll try figuring out that one myself.